DE112013007109B4 - Packages for micro-electromechanical system devices and method of making the package for micro-electromechanical systems devices - Google Patents

Abstract

A housing (11) for microelectromechanical system devices, comprising:
- a substrate (12) with a first substrate plane (13) and a second substrate plane (14), which is arranged on the opposite side of the substrate (12) from the first substrate plane (13), and with a first (15) and a second (15') connection contact, which are arranged on the first substrate level (13),
- a MEMS device (18) having a first (19) and a second (19') contact pad arranged on a front side of the MEMS device, the MEMS device (18) being on the first substrate level by means of flip chip technology (13) is mounted, the front side is opposite the first substrate level (13) and the first (19) and second (19') contact points are electrically connected to the first (15) and second (15') connection contact, as a result of which an intermediate space (21 ) is formed between the MEMS device (18) and the first substrate level (13),
- a film made of a non-evaporable getter material (22) which is arranged at least partially in the intermediate space (21) on the first substrate plane (13),
- a cap structure (23) encapsulating the MEMS device (18) by being sealed to the first substrate level (13) and enclosing the MEMS device (18) between the first substrate level (13) and the cap structure (23). ,
- a third (16) and a fourth (16') connection contact, which are arranged on the second substrate level (14), wherein the third (16) connection contact is electrically connected to the first (15) connection contact and the fourth (16') terminal is electrically connected to the second (15') terminal, and
- The substrate (12) further comprises a fifth (28) and a sixth (28') connection contact, which are arranged on the first substrate level (13), a seventh (29) and an eighth (29') connection contact, which are arranged on the second Substrate plane (14) are arranged, wherein the seventh (29) connection contact is electrically connected to the fifth (28) connection contact and the eighth (29') connection contact is electrically connected to the sixth (28') connection contact and the film consists of non-evaporable getter material (22) is connected to the fifth (28) and sixth (28') connection contact.

Description

This invention relates to microelectromechanical systems (MEMS) such as SAW devices and BAW/FBAR resonators or filters, or sensors. More particularly, this invention relates to packages for MEMS devices and methods of making the same.

Microelectromechanical systems (MEMS) typically include micromechanical elements, actuators, and electronic components. After fabrication, a MEMS device may be housed in a chamber to protect the mechanical structure from damage and contamination with contaminants that may cause performance degradation, behavioral variations, or failure of the MEMS device.

For example revealed JP 2029017A describe a packaging method for a surface acoustic wave device in which a wire-bonded SAW device and a wire-bonded line-active semiconductor getter are vacuum-sealed in a package.

CN 102040186A relates to a high vacuum packaging method for leadless ceramic chip carriers (LCC) in which a MEMS device is packaged using the steps of plasma cleaning, eutectic surface mounting, contact bonding, getter activation and eutectic sealing.

The US patent application US 2011/0290552 A1 discloses a packaging structure for MEMS devices comprising an interferometric modulator array formed on a substrate and encapsulated between the substrate and a back plane, wherein a chemically active getter material is placed in a cavity between the back plane and the substrate above the interferometric plane Modulator arrangement is positioned.

The US patent application U.S. 2011/0165718 A1 discloses a method of fabricating microelectromechanical systems having mechanical structures encapsulated in a chamber using thin film wafer level packaging techniques, wherein an integrated getter region and/or an expanded volume of the chamber is provided by forming gaps, trenches and/or or discs are formed in an edge region of the MEMS device.

The DE 102 38 523 A1 relates to an encapsulated component in which a gap is provided between a carrier substrate and the active surface of a chip and which contains a chip which is arranged on top of the carrier substrate and is electrically and mechanically connected thereto by means of bumps or other electrically conductive connections.

The JP H10-163 798 A discloses the provision of a surface acoustic wave (SAW) element and inexpensive electronic parts using the same, so that not only sealing work in an inert gas is unnecessary, but also stable characteristics can be provided using the process technology of ordinary semiconductor production.

The processes for manufacturing these types of MEMS packages are relatively complex and expensive. Furthermore, conventional MEMS packages typically result in a relatively large overall size of the package compared to the dimensions of the MEMS itself, and therefore do not meet current needs for smaller MEMS components required in miniaturized circuits and devices with higher component density.

It is therefore an object of the present invention to provide an improved package for microelectromechanical system devices which overcomes or at least reduces some of the disadvantages of the above prior art.

The independent product and method claims provide a solution to the above problems. The dependent claims provide further preferred embodiments.

The invention provides a housing for microelectromechanical system devices, which comprises a substrate having a first substrate level and a second substrate level lying on the opposite side of the substrate from the first substrate level, and having a first and a second connection contact which are arranged on the first substrate level . A MEMS device with a first and a second contact pad, which are arranged on a front side of the MEMS device, is mounted using flip chip technology on the first substrate level so that the front side of the MEMS device faces the first substrate level and the first and second Pad are electrically connected to the first and second terminal pads, thereby forming a gap between the MEMS device and the first substrate level. A film of non-evaporable getter material is at least partially interspaced on the first substrate plane. A cover structure encapsulates the MEMS device, by being sealed to the first substrate level and enclosing the MEMS device between the first substrate level and the cap structure. A third and a fourth connection contact are arranged on the second substrate level, the third connection contact being electrically connected to the first connection contact and the fourth connection contact being electrically connected to the second connection contact. Furthermore, the substrate comprises a fifth and a sixth connection contact, which are arranged on the first substrate level, and a seventh and an eighth connection contact, which are arranged on the second substrate level, the seventh connection contact being connected to the fifth connection contact and the eighth connection contact being connected to the sixth connection contact is electrically connected and wherein the film of non-evaporable getter material is connected to the fifth and sixth terminal contacts.

As used herein, non-evaporable getter (NEG) material means a reactive material that has the ability to combine chemically or by absorption with gas molecules. In particular, it is to be understood that the term "non-evaporable getter" is used herein to distinguish from "evaporable getters", i.e. the non-evaporable getter material remains in a solid state during deposition or activation, rather than being vaporized and condensed onto a surface become.

MEMS devices such as BAW or FBAR resonators or filters can be very sensitive to the absorption or adsorption of gas or moisture on one of their surfaces. This phenomenon can function as a mass loading effect resulting in, for example, a frequency shift of the device. Furthermore, it can cause corrosion of thin conductor lines of, for example, SAW devices, and thus a loss of performance or failure of the device. While packages for MEMS devices can be sealed under vacuum, the inventors of the present invention have noted that this does not prevent the adsorption or absorption of molecules that outgas or are desorbed from materials contained within the package or from the outside into a non-hermetically sealed package diffuse. By placing a film of non-evaporable getter material within the MEMS package, the inventors of the present invention achieve the maintenance of a high vacuum within the package, thereby advantageously reducing or preventing the adverse effect of gas contaminants on the MEMS device. In this way, higher accuracy of the electrical and mechanical properties of the MEMS device and improved long-term performance can be achieved. At the same time, the package assembly of the present invention is much smaller than conventional package assemblies that use, for example, wire bonding to connect the MEMS device to external circuitry.

In the embodiment of the present invention, the package for MEMS devices further includes third and fourth connection pads arranged on the second substrate level. The third terminal is electrically connected to the first terminal and the fourth terminal is electrically connected to the second terminal. For example, the third and fourth contact pads may be adapted to connect the MEMS device package to external circuitry. In particular, the third and fourth connection contacts may be suitable for surface mounting the package for MEMS devices on a printed circuit board. In this way, the space requirements of the device package can be significantly reduced, which in turn allows miniaturization of circuits and devices and also reduces manufacturing costs.

The MEMS device may also include other pads. For example, there may be pads for an electrical ground connection, an antenna connection, a signal input, and/or a signal output.

In some embodiments, the substrate includes at least one ceramic layer. Preferably, the substrate comprises a ceramic device having a stack of at least two ceramic layers and at least one electrode layer sandwiched between the ceramic layers in the stack. The substrate can further comprise vertical electrical connections which connect the connection contacts on the first substrate level to the connection contacts on the second substrate level and/or the at least one electrode layer. In this way, a particularly reliable electrical connection of the device housing to an external circuit can be achieved.

The ceramic device may also include a plurality of ceramic layers and electrode layers disposed between the ceramic layers. In addition, the ceramic device may further include passive electrical elements, such as resistors, capacitors, and/or inductors. In this way, a high level of integration and functionality of the device can be achieved by the housing, while at the same time the overall dimensions of the housing are advantageously kept small.

Preferably, the ceramic device is a monolithic multi-layer component having a stack of co-sintered ceramic layers and at least one electrode layer between the ceramic layers. For example, the monolithic, multilayer ceramic component may be a high temperature single-fired ceramic (HTCC) formed at a sintering temperature of about 1600°C. Preferably, the monolithic multilayer component is a low-temperature single-fired ceramic formed at a sintering temperature of about 1000°C or less. The electrode layers and terminal contacts may comprise copper, gold and/or silver, for example.

In the embodiment of the invention, the package for MEMS devices further comprises fifth and sixth contact pads arranged on the first substrate level and seventh and eighth contact pads arranged on the second substrate level. The seventh connection contact is electrically connected to the fifth connection contact; the eighth connection contact is electrically connected to the sixth connection contact. The film of non-evaporable getter material is electrically connected to the fifth and sixth terminal pads. This arrangement makes it possible, for example, to apply an electric current to the film of non-evaporable getter material via the connection contacts. For example, the electric current can be used to locally heat the NEG film to activate the NEG via Joule heating. In an alternative embodiment, a heating component that converts electrical current to heat may be electrically connected to the fifth and sixth terminal contacts, and the non-evaporable getter material may be placed in thermally conductive contact with the heating component.

In this way, the NEG material can be indirectly thermally activated by applying an electrical current to the heating component through the terminal contacts. Such arrangements may be used, for example, in embodiments where the NEG material is not electrically conductive.

The cover structure may be hermetically sealed to the first substrate level or non-hermetically sealed to the first substrate level. Preferably, the cover structure is hermetically sealed to the first substrate level.

In one embodiment, the cover structure comprises a first coating with a polymer film that seals the first substrate level in a first edge region and encloses the MEMS device between the first substrate level and the polymer film. For example, the polymer film may comprise a polyimide film. A suitable example is a poly(4,4'-oxydiphenylene pyromellitimide) film such as Kapton.

In one embodiment, the cover structure comprises at least one further coating arranged over the polymer film and sealed to the first substrate level in a second edge area around the first edge area and the MEMS device between the first substrate level, the polymer film and the at least one further coating of an inorganic material layer. For example, the at least one other coating may include a metallic coating, a silicon oxide coating, a silicon nitride coating, or combinations thereof.

In one embodiment, the non-evaporable getter material includes Zr, V, Ti, Fe, or combinations thereof. In certain examples, a zirconium-vanadium-titanium alloy or a zirconium-vanadium-iron alloy may be present. With these materials, the activation of the NEG material can be achieved at relatively low temperatures, so that the thermal degradation of the package during the thermal activation of the NEG is effectively prevented when the NEG activation takes place inside the package.

In one embodiment, the MEMS device is selected from a group consisting of a SAW device, a BAW resonator, and an FBAR resonator. In particular, the MEMS device is a BAW resonator or an FBAR resonator.

1. A) das Bereitstellen des oben beschriebenen Gehäuses für mikroelektromechanische Systemvorrichtungen,
2. B) das Versiegeln des Gehäuses,
3. C) das Aktivieren des nicht verdampfbaren Getter-Materials.

In a second aspect, the invention provides a method of manufacturing the package for microelectromechanical system devices. The procedure includes the following steps:

1. A) providing the housing for microelectromechanical system devices described above,
2. B) sealing the housing,
3. C) activating the non-evaporable getter material.

• A1) das Bereitstellen des Substrats,
• A2) das Anordnen des Films aus dem nicht verdampfbaren Getter-Material auf der ersten Substratebene.

In one embodiment, method step A) comprises the following sub-steps:

• A1) providing the substrate,
• A2) arranging the film of non-evaporable getter material on the first substrate level.

Process step A2) can include, for example, sputter deposition, physical vapor deposition, printing, dip coating with or spin coating with the non-evaporable getter material(s) on the first substrate layer.

In one embodiment, the method A2) further comprises the sub-step A2′) of structuring the film made of the non-evaporable getter material. In order to achieve the patterning of the film of non-evaporable getter material, a patterned masking layer may be placed on the first substrate level before the film of non-evaporable getter material is placed on the first substrate level. The masking layer may have openings which expose the first substrate plane for the film of non-evaporable getter material during deposition. The masking layer is removed from the first substrate level after deposition of the film of non-evaporable getter material, thereby removing that portion of the NEG material that was placed on the masking layer. The patterning of the film of non-evaporable getter material can also be achieved by etching the film of evaporable getter material after deposition. Alternatively, a combination of a masking layer and post-deposition etching of the film of non-evaporable getter material may be used.

In one embodiment, a vacuum is maintained in method step B) and/or in method step C). Suitable vacuum conditions include, for example, high vacuum conditions with a pressure of max. 10-3 mbar (10-3 hPa) or lower. A pressure of max. 10-4 mbar (10-4 hPa) or lower is even more preferred.

In a further embodiment, method step C) comprises thermally activating the film of non-evaporable getter material at a temperature between 150°C and 500°C, preferably between 200°C and 400°C.

With the fifth, sixth, seventh, and eighth terminals in place, thermally activating the film of non-evaporable getter material can be achieved using ohmic heating by applying an electrical current to the film of non-evaporable getter through the fifth through eighth terminals getter material is created. In this manner, substantially selective heating of the NEG film is achieved such that thermal degradation of more temperature sensitive components of the MEMS device package, such as the cap structure, is advantageously prevented. In embodiments where the fifth, sixth, seventh, and eighth contact pads are not present, thermal activation of the film of non-evaporable getter material may also be achieved by heating the MEMS device package to a temperature that activates the film of non-evaporable getter material but does not degrade the case. This type of activation can take place in an oven, for example.

character list

• 1 zeigt einen Querschnitt eines grundlegenden Beispiels eines Gehäuses für MEMS-Vorrichtungen,
• 2 zeigt einen Querschnitt eines Gehäuses für MEMS-Vorrichtungen mit einer Deckstruktur, welche eine erste und zweite Beschichtung umfasst,
• 3 zeigt einen Querschnitt einer Weiterentwicklung des Gehäuses für MEMS-Vorrichtungen aus 2 mit einem elektrisch verbundenen Film aus nicht verdampfbarem Getter-Material gemäß der Erfindung.

In the following schematic figures, examples of packages for microelectromechanical system devices are shown. The examples in the figures are to be understood as illustrative only and are not intended to limit the scope of the invention to specific details. Individual elements in the figures may be identified with reference numbers. However, for the sake of clarity, recurring items cannot be labeled more than once.

• 1 shows a cross-section of a basic example of a package for MEMS devices,
• 2 shows a cross section of a housing for MEMS devices with a cover structure comprising a first and second coating,
• 3 Figure 12 shows a cross-section of a further development of packaging for MEMS devices 2 with an electrically connected film of non-evaporable getter material according to the invention.

1 Figure 12 shows an example of a basic package 11 for MEMS system devices of the present invention. The housing comprises the substrate 12 with a first substrate level 13 and a second substrate level 14 which is opposite to the first substrate level. A first and second connection contact 15, 15' are arranged on the first substrate level, and a third and fourth connection contact 16, 16' are arranged on the second substrate level. The substrate comprises a ceramic device having a stack of two ceramic layers and an electrode layer sandwiched between the ceramic layers. Vertical electrical connections 17, 17' go through the ceramic layers and electrically connect the connection contacts on the first substrate level to the electrode layers and the connection contacts on the second substrate level. The MEMS device 18 with a first and a second pad 19,19' arranged on a front side of the MEMS devices are mounted on the first substrate level using flip-chip technology, so that the front side is opposite the first substrate level. The first and second pads are electrically connected to the first and second terminal pads. For example, solder balls 20, 20' can be used to perform the connection of the pads and the terminal contacts. A gap 21 exists between the MEMS device and the first substrate level. A film of non-evaporable getter material 22 is placed at least partially in the gap. The MEMS device is encapsulated between the substrate and a cap structure 23 which is arranged over and around the MEMS device and is sealed to the first substrate level 13 .

2 FIG. 12 basically shows the housing of the MEMS device 1 in a further embodiment in which the cover structure comprises a first coating which is a polymeric film 24 and a second coating 25 which is disposed over the polymeric film. The polymer film seals the first substrate level 13 in a first edge region 26 and encapsulates the MEMS device between the first substrate level and the polymer film. The second coating 25 is sealed to the first substrate level 13 in a second edge region 27 and encapsulates the MEMS device between the first substrate level 13, the polymer film 24 and the second coating 25.

3 shows a cross section of a package for MEMS devices according to the invention, wherein the substrate 12 comprises a fifth and sixth connection contact 28, 28', which are arranged on the first substrate level 13, and a seventh and eighth connection contact 29, 29', which are arranged on the second substrate level 14 arranged wind, wherein the film made of the non-evaporable getter material 22 with the fifth and sixth connection contact 28, 28 'and vertical electrical connections 30, 30' with the seventh and eighth connection contact 29, 29 ', which on the second substrate plane 14 are arranged, is electrically connected. In this example, an electrical current can be selectively applied to the NEG film 22 via the terminal contacts and vertical electrical connections to locally heat the NEG film to activate it without risk of thermal degradation of other components of the device housing .

Reference List

11

Packages for MEMS devices

12

substrate

13

first substrate level

14

second substrate level

15, 15'

first connection contact, second connection contact

16, 16'

third connection contact, fourth connection contact

17,17'

vertical electrical connections

18

MEMS device

19, 19'

first point of contact, second point of contact

20,20'

solder ball

21

space

22

Film of non-evaporable getter material

23

deck structure

24

polymer film

25

second coating

26

first border area

27

second edge area

28,28'

fifth connection contact, sixth connection contact

29,29'

seventh connection contact, eighth connection contact

30,30'

vertical electrical connections

Claims (17)

Housing (11) for microelectromechanical system devices, comprising: - a substrate (12) with a first substrate level (13) and a second substrate level (14) which is arranged on the opposite side of the substrate (12) from the first substrate level (13), and having a first (15) and a second (15') connection contact arranged on the first substrate level (13), - a MEMS device (18) having a first (19) and a second (19') contact point, which are arranged on a front side of the MEMS device, wherein the MEMS device (18) is mounted by means of flip chip technology on the first substrate level (13), the front side faces the first substrate level (13) and the first (19) and second (19') pad are electrically connected to the first (15) and second (15') terminal contact, thereby forming a gap (21) between the MEMS device (18) and the first substrate plane (13), - a film of one not deserve acetable getter material (22), which is on the first substrate plane (13) at least partially in the intermediate space (21) is arranged, - a cover structure (23) which encapsulates the MEMS device (18) by being sealed to the first substrate level (13) and the MEMS device (18) between the first substrate level (13) and the cover structure ( 23) includes, - a third (16) and a fourth (16') terminal contact arranged on the second substrate level (14), the third (16) terminal contact being electrically connected to the first (15) terminal contact and the fourth (16') connection contact is electrically connected to the second (15') connection contact, and - the substrate (12) also has a fifth (28) and a sixth (28') connection contact, which are arranged on the first substrate level (13), comprises a seventh (29) and an eighth (29') connection contact which are arranged on the second substrate level (14), the seventh (29) connection contact being connected to the fifth (28) connection contact and the eighth (29') connection contact being connected to the sixth (28') connection contact akt is electrically connected and wherein the film of non-evaporable getter material (22) is connected to the fifth (28) and sixth (28') terminal contacts. A package (11) for MEMS devices (18) according to the preceding claim, wherein the substrate (12) comprises at least one ceramic layer. A package (11) for MEMS devices (18) according to any one of the preceding claims, wherein the substrate (12) comprises a ceramic device having a stack of at least two ceramic layers and at least one electrode layer disposed between the ceramic layers in the stack. A package (11) for MEMS devices (18) according to any one of the preceding claims, wherein the cover structure (23) is hermetically sealed to the first substrate level (13). Housing (11) for MEMS devices (18) according to any one of the preceding claims, wherein the cover structure (23) comprises a first coating with a polymer film (24) which seals to the first substrate plane (13) in a first edge region (26). and enclosing the MEMS device (18) between the first substrate plane (13) and the polymeric film (24). Housing (11) for MEMS devices (18) according to the preceding claim, wherein the cover structure (23) comprises at least one further coating which is arranged over the polymer film (24) and is connected to the first substrate plane (13) in a second edge region ( 27) is sealed around the first edge region (26) and encloses the MEMS device (18) between the first substrate plane (13), the polymer film (24) and the at least one further coating. Housing (11) for MEMS devices (18). claim 6 , wherein the at least one further coating comprises a metallic coating, a silicon oxide coating, a silicon nitride coating or combinations thereof. A package (11) for MEMS devices (18) according to any one of the preceding claims, wherein the non-evaporable getter material comprises Zr, V, Ti, Fe or combinations thereof. A package (11) for MEMS devices (18) according to any one of the preceding claims, wherein the MEMS device (18) is selected from a group consisting of a SAW device, a BAW resonator and an FBAR resonator. Method for producing the housing (11) for microelectromechanical system devices, which comprises the following method steps: A) providing the housing (11) for microelectromechanical system devices according to one of Claims 1 - 9 , B) sealing the housing (11), C) activating the non-evaporable getter material. Method according to the preceding claim, wherein method step A comprises the following sub-steps: A1) providing the substrate (12), A2) arranging the film of non-evaporable getter material on the first substrate plane (13). Method according to the preceding claim, wherein method step A2) comprises sputter deposition of, physical vapor deposition of, printing of, dip coating with or spin coating with the non-evaporable getter material(s). procedure after claim 11 or 12 , wherein the method step A2) further comprises the sub-step A2') of structuring the film made of the non-evaporable getter material (22). Method according to the preceding claim, wherein the sub-step A2') further comprises at least one of the following sub-steps: A2'') arranging a masking layer on the first substrate level (13), the masking layer having openings which the first exposing the substrate plane (13) and removing the masking layer after arranging the film of non-evaporable getter material (22); A2''') patterning the film of non-evaporable getter material (22) by etching the film of non-evaporable getter material (22) after placement. Procedure according to one of Claims 10 - 14 , A vacuum being maintained in process step B) and/or in process step C). Procedure according to one of Claims 10 - 15 wherein step C) comprises heat activating the film of non-evaporable getter material (22) at a temperature between 150°C and 500°C, preferably between 200°C and 400°C. The method of the preceding claim, wherein the fifth (28), sixth (28'), seventh (29) and eighth (29') terminal contacts are present and wherein heat activating the film of non-evaporable getter material (22) comprises applying applying an electrical current across the terminal contacts to the film of non-evaporable getter material (22).

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